Abstract: An apparatus which is used for non-contact electrical measurement and physical alteration of certain characteristics and properties of electronic conductor devices. The apparatus includes a focused source of ultraviolet light which is capable of micron and sub-micron resolution.In the measurement mode the apparatus measures the energy of electrons ejected from a measurement site by the UV beam. This measurement is accomplished at a nulling/repelling device. In the alteration mode, the focused UV light beam interacts with various compounds, for example chemical gases, to create a selective reaction at specific locations at the surface of the device being operated upon.The measurement function can be related to voltage, current, temperature or the like and may be either qualitative or quantitative while being made in a non-contact basis.